Impervious membrane oil storage system

ABSTRACT

Storage system for oil in impervious membrane envelopes comprising a water basin with communicating compartments each for one container, the system being such that optimal fire protection is achieved with minimal dimensions.

ilnitefl States Patent Leguijt 451 May 29, 11973 [5 IMPERVIOUS MEMBRANEOIL [56] References Cited STORAGE SYSTEM UNITED STATES PATENTS [75]Inventor: 3805 Leguijt, Dordreih" Nether 3,052,380 9/1962 Prins 14/05 '1lands 3,067,712 12/1962 Doerpinghaus... ..114/74 T Assignee: Mannesmanh(Nederland) N.v., 3,1 QUBSC ..1 T Dintelmond (Gem. g 3,435,793 4/1969Shurtleff ..1 14/0.5 T Netherlands Primary Examiner Duane A. RegerAssistant Examiner-Stuart M. Goldstein [22] Flled 1971 Att0rney-Waters,Roditi, Schwartz & Nissen [21] App1.No.: 128,033

[57] ABSTRACT [52'] US. Cl ..1l4/0.5 T, 1 14/74 T Storage system for oilin impervious membrane en- [51 Int. Cl. ..B63b 35/00 velopes comprisinga water basin with communicating [58] Fieldof Search.. ..1 14/0.5 T, 74T; compartments each for one container, the system 61/1 F being suchthat optimal fire protection is achieved with minimal dimensions.

10 Claims, 5 Drawing Figures PATENTEEHAYZQIBH SHEET 2 [IF 2 IMPERVIQUSMEMBRANE OIL STORAGE SYSTEM The invention relates to a storage systemfor a fluid with a specific gravity lower than I, for example crude oil,in which the fluid, confined in a container manufactured with the use offlexible material, floats on water.

Such a storage system is described in British Pat. No. 878,158. If insuch a storage system the shell surrounding the oil goes out of order,any leakage oil will spread over a large surface area, which from thestandpoint of fire protection, is very dangerous. In the conventionalsystem use is, moreover, made of mooring cables, so that a large spacemust be available for the storage.

The object of the invention is to improve a storage system of the typedescribed in which the protection against fire hazard is maximal and theutilization of space optimal.

According to the invention, the storage system is to this endcharacterized by means for restricting the contact surface with theoutside air of oil flowing out in case of container fracture.

According to the invention, use is made of a basin in which, by means ofpartitions, a plurality of intercommunicating compartments are formedvia a passage located adjacent the basin bottom, each being adapted toreceive a flexible container.

In case of storage variation in one or more of the flexible containersin the basin, water can flow into or out of the compartment via thepassages located adjacent the basin bottom, the arrangement being suchthat the level in all the compartment of the basin remains equal.Therefore, the partitions need not have a specific height above thewater level.

These partitions have in addition a function which can best be comparedwith the well-known embankments around above-ground storagetanks. If aflexible container goes out of order, the oil only flows out over thesurface of the respective compartment.

To prevent that outflowing oil form one specific compartment reaches oneor more other compartments via the communication passage, thecompartments according to the invention may each communicate with anequalizing duct and the latter via an overflow drain which is located onsuch a level that in case of container fracture the light layer of fluidformed in the compartment and floatingon water is located above. thedrain opening, so that only water displaced by the fluid can escapethrough the drain.

So as to minimize the surface over which leaking oil in a compartmentspreads and to also optimally use the space available for the storage,the horizontal peripheral configuration of each compartment according tothe invention may correspond substantiallyv to that of a filled,flexible container freely floating therein.

To prevent a fire formed, in one compartment from spreading to othercompartments, according to the invention the top edges of the partitionsbetween the compartments may be provided with upwardly extending firescreens.

When oil in a specific compartment has flown out of the flexiblecontainer and, in the compartment, forms maining part can betransmitted, according to the invention, via cables or chains attachedto the respective upper ledges to other partitions. In view of this, thestructure of each partition can remain relatively light in weight.

In order to impart to the side of the container which is exposed-to theouter air a flat and therefore less vulnerable shape, a weighting layermay be mounted on the flexible container according to the invention.

According to the invention a chain netting may also be suspended fromthe upper ledges of two partitions defining a reservoir, supplementaryto or in lieu of th weighting layer and in lieu'of the cables.

According to the invention, use can further be made in the storagedevice of containers each in the form of a closed envelope having astorage capacity'which is at most equal to the volume of the compartmentportion located above the communication opening in the partition.According to the invention, the envelope may be rectangular in an emptystate. For optimal space utilization the envelope may have the samelength and width in an empty condition asthe compartment.

Additionally in connection with fire protection, in each compartment atleast the container may be covered by a layer of fireproof material.Moreover, the bottom side of the closed envelope may also be providedwith a layer having insulating properties.

The envelope, which in and empty state is rectangular, will in thefilled condition be elongated with a cross-section which is more or lessin the shape of an ellipse. Although there is no objection to the filledenvelope resting with its bottom surface on the bottom, according to theinvention each envelope is preferably supported along the bottom surfaceby'a layer of floating material, for instance a cork mat, so that theenvelope will also float in an empty state. 7

In order to explain the invention, an exemplary embodiment of thestorage system will be described with reference to the drawing.

FIG. 1 is a top view of a basin for a plurality offlexible containers;

FIG. 2 is a sectional view on the line II-II in FIG. 1; FIG. 3 is asectional view on the line IIIIII in FIG.

FIG. 4 shows a sectional view of an oil-filled container floating onwater and FIG. 5 shows a graphic approach for the crosssectionalconfiguration of a filled container.

In the drawing, in particular FIG. 1, a rectangular basin 1, whosedimensions may be in practice 450 X in, measured along the edge by anedge line 2 having a slope of l 2 3. The slope of the line 2 is definedon the outer side by a basin edge 3 and on the inner side by a marginalbaffle 4. The basin is divided by a plurality of partitions 5 into anumber of compartments6. The partitions 5 extend, just as the marginalbaffles 4, into the bottom 7 of the reservoir. In the marginal baffle 4located along the longer side of the reservoir there is provided, ineach compartment, an overflow drain 8, whose inlet on the compartmentside is adjacent the basin bottom 7.

FIG. 3 shows in cross-section a compartment 6 having therein an envelope9 manufactured of flexible material, for instance impregnated nylonfabric. The envelope which is filled, for example with crude oil, floatsin the water in the compartment, with a part of the filled envelopeextending above the water. The horizontal peripheral configuration ofthe filled envelope substantially corresponds with the rectangular shapeof the compartment 6.

On the basis of an envelope length of 390 m, a storage capacity may beattained of about 450,000 m.

If the dimensions of the compartment in which the filled envelope floatsare 100 X 390 390,00 m 450,000 m 011 will flow out over this surface ifthe envelope goes out of order. This 011 then forms an oil layer (whichremains covered by the envelope which has meanwhile been emptied) havinga thickness of 1 1.54 m, of which 1.73 m remains above the water-line.At the water level there is therefore exerted a static pressure of 1.47ton/m on the partitions. The total pressure is 8.48 ton per meter ofwall. This load is partly discharged via the wall to the bottom and theother part of the load via the upper ledge and a chain netting 11 to theopposite partition. In view of this chain netting, which also serves tomaintain the envelope in position, the construction of the partition canremain relatively light.

The inlet of the overflow drain 8 on the side of the compartment must beso far down below the water level that no oil of the layer floating inthe reservoir can escape via the drain to the equalizing duct 12. Theequalizing duct 12 is located between the marginal baffle 4 and thebasin edge 3 along one or both longer sides of the basin.

The total storage capacity of the entire basis would, in case of ninecompartments, be 9 X 450,000 m 4 X 10 m Suppose that in practice thetotal storage variation is restricted to 10 percent thereof, in effect400,000 m, the variation in water level would be consequently be limitedto less than one meter. Discharge or intake of water in the basin willtherefore frequently not be necessary although there must be considereda possibility of this contingency arising.

FIG. 4 shows a section of an envelope 9 which is filled with oil andfloating on water. In an empty state the envelope is rectangular andmanufactured preferably of impregnated nylon fabric. Also applicable isthe material of which the Dunlop dracones are made, or the NRDC made byGordon Low. In an empty state lying on the water, the envelope rests ona layer of floating material 13 (for instance cork mats), while the topside thereof is covered with a layer of heavier material. Both the topside and the bottom side may have insulating properties, while the toplayer may also be fireproof.

If the envelope is pumped full of oil, its cross-section will take theshape as shown in FIG. 4. The specific cross-sectional shape of thefilled envelope and the fact that part thereof extends above'water arethe result of the fact that oil floating on water tends to spread overthe largest possible surface and that each displaced m of water iscapable of supporting one ton of oil, respectively.

At points A and B the pressure difference between the inner space of theenvelope and the outer side is substantially nil and the curve of theenvelope wall is 0. At the water-line the curve is maximal, because atthis level the difference in static pressure of water and oil ishighest. The static pressure of the oil varies according to the straightline A D and the compensating water pressure according to the straightline C D.

In case of a height A C of from 2 to 2.5 m a maximum static pressure ofabout 2 tons/m is attained. Taking this value as a starting point theenvelope reservoir is therefore full if at the water-line a staticpressure of 2 tons/m prevails in the interior of the envelope. Fordifferent specific weights of oil the following values for A C, A B andC D have been found:

A C A B C D Specific weight 0.8 3 2.50 12.5 10 m Specific weight 0.85 32.35 15.69 13.34 m Specific weight 0.9 3 2.22 22.22 20 m It appears fromthe table that the envelope has a greater storage capacity as the oilbecomes heavier.

As it is permissible that the envelope rest with the bottom surfacethereof on the bottom in the middle of the compartment, the depth of thebasin may be maintained, for instance, at 15 m.

F IG. 5 graphically shows in which manner the capacity of an envelopewith a periphery of 200 m, (empty with a width of m) can be reached.Since the capacity is dependent upon the specific weight, a calculationwill be made, by way of example, for an oil filling having a specificweight of 0.85. In FIG. 5 the distance A C 2,35 m and the distance A B15.69 m. The actual cross-sectional shape of the envelope ranges betweentwo extremes, namely a rectangular section PQRS, whose width P Q 84.31m, and a lozengelike cross-sectional shape, ALBK, whose width K L 98.16m. In both cases the periphery is equal to 200 The surface area of therectangle is 1323 m and that of the lozenge figure 770 m The shape ofthe envelope approaches, as regards surface area, the rectangular figuremore closely than the lozenge figure and a section of 1200 m isplausible. Per meter of length the envelope may therefore contain 1200 moil.

It is clear that the invention is not limited to the above embodiment,but that variants are possible within the framework of the invention.For example, instead of a closed flexible envelope a domeshapedcontainer of flexible material with open lower side may be used, whosehorizontal dimensions correspond to those of a compartment.

I claim:

1. A device for storing a fluid with a specific gravity lower than 1,for instance crude oil, comprising a container of flexible materialcontaining said oil, a receptacle laterally encompassing said containerand having a substantially corresponding circumferential shape as thecontainer, a quantity of water being provided in said receptacle forfloatingly supporting said fluidcontaining container thereon, saidreceptacle forming a water basin; partition means dividing said basininto a plurality of passages having communicating compartments locatedadjacent the bottom of the basin, each said compartment being adapted toaccommodate one said flexible container.

2. A device according to claim 1, comprising equalizing duct meanscommunicating each of said compartments, said duct means including anoverflow drain on a predetermined level, whereby in case of containerfracture, the light specific gravity fluid layer formed in thecompartment and floating on water is located above the drain opening, sothat only water displaced by the fluid can escape through the drain.

3. A device according to claim 1, comprising a plurality of saidflexible containers in juxtaposed relation, said container beingrectangular in configuration when empty, each said compartment beingcorrespondingly rectangular and having the same peripheral dimensions asthe containers.

4. A device according to claim 1, comprising upright fire screen meansbeing positioned along the top edges of the partition means intermediatethe compartments.

5. A device according to claim 3, comprising guy ropes connecting theupper ledges of each partition means to other of said partition means.

6. A device according to claim 3, comprising chains connecting the upperledges of each partition means to other of said partition means.

said layer being constituted of at least one cork mat.

1. A device for storing a fluid with a specific gravity lower than 1,for instance crude oil, comprising a container of flexible materialcontaining said oil, a receptacle laterally encompassing said containerand having a substantially corresponding circumferential shape as thecontainer, a quantity of water being provided in said receptacle forfloatingly supporting said fluid-containing container thereon, saidreceptacle forming a water basin; partition means dividing said basininto a plurality of passages having communicating compartments locatedadjacent the bottom of the basin, each said compartment being adapted toaccommodate one said flexible container.
 2. A device according to claim1, comprising equalizing duct means communicating each of saidcompartments, said duct means including an overflow drain on apredetermined level, whereby in case of container fracture, the lightspecific gravity fluid layer formed in the compartment and floating onwater is located above the drain opening, so that only water displacedby the fluid can escape through the drain.
 3. A device according toclaim 1, comprising a plurality of said flexible containers injuxtaposed relation, said container being rectangular in configurationwhen empty, each said compartment being correspondingly rectangular andhaving the same peripheral dimensions as the containers.
 4. A deviceaccording to claim 1, comprising upright fire screen means beingpositioned along the top edges of the partition means intermediate thecompartments.
 5. A device according to claim 3, comprising guy ropesconnecting the upper ledges of each partition means to other of saidpartition means.
 6. A device according to claim 3, comprising chainsconnecting the upper ledges of each partition means to other of saidpartition means.
 7. A device according to claim 3, comprising chainnetting being suspended from the upper ledges of two partition meansdefining a compartment.
 8. A device according to claim 3, comprising alayer of fire-resistant material covering at least the container in eachsaid compartment means.
 9. A device according to claim 3, comprising aninsulating layer being provided on the bottom of each said flexiblecontainer.
 10. A device according to claim 3, comprising a layer offloating material being positioned below each said flexible container soas to support the bottom thereof, said layer being constituted of atleast one cork mat.